For storage and transport purposes, it is customary to place such biopharmaceutical fluids in bags having a wall made of plastic that is flexible, closed, and sterile. It is essential that such bags be fluidtight when they receive biopharmaceutical fluid prior to use or during use of the biopharmaceutical fluid, or at least have a satisfactory level of fluidtightness, so that their possible content is preserved from any deterioration originating externally to the bag, such as contamination. It is therefore necessary to be able to easily detect any loss of integrity of the bag before, during, or after use.
Various methods are currently known for verifying the integrity of a bag suitable for containing a biopharmaceutical fluid. A first known method consists of a physical test to determine if the wall of the bag has a leak or hole. Patent EP 2,238,425 describes a method in which the pressure inside an empty and sterile bag is increased between two plates which limit its expansion. A porous material is placed between the wall of the bag and each plate to prevent the contact of the wall and the expansion-limiting plates from concealing any leaks. The bag is inflated and then the variation of the pressure applied to the two plates as a function of the pressure applied inside the bag is analyzed. If there is bag leakage, the pressure applied to the plates of the test device falls over time below a given threshold, which allows concluding a loss of integrity.
Patent US 2014/0165707 discloses another method for testing the integrity of a bag. The bag is placed in a compartment and a structured permeable reception layer is placed between the bag and the compartment. The bag is then connected to a source of filling fluid in order to generate a predetermined positive pressure therein. Then the pressure variation in the bag is analyzed to determine whether it is fluidtight and therefore intact. Similarly, also known are U.S. Pat. No. 8,910,509 or US 2014/0083170 which describe a portable device for verifying the integrity of a bag wherein the bag is filled with air, preferably sterile, before measuring the pressure therein in order to detect any loss of integrity.
Finally, there are also other known methods for verifying integrity using an inert tracer gas. For example, the “Helium Integrity Testing” method (HIT®) involves placing an entire bag in a container and then creating a vacuum in the container once it is closed around the bag. A specific amount of helium is then introduced into the bag. If there is bag leakage, a mass spectrometer detects the presence of helium in the container outside the bag.
These physical test methods, when they are implemented after the bag has been used, may not be able to detect holes in the wall of the bag if they are less than two micrometers, as the holes may be obstructed by residual drops of biopharmaceutical product. In addition, detection of a leak due to a hole smaller than 2 microns is difficult to detect because the leak is often too small to distinguish from the background leakage inherent to the bag. However, it is known that a microorganism can pass through a hole smaller than this size, in particular a hole as small as 0.2 micrometers. The use of the physical test methods described above therefore does not ensure the absence of microbial entry into the bag.
Furthermore, such methods require introducing a gas or fluid into the bag during the integrity verification. These methods therefore cannot be carried out when the bag is filled with biopharmaceutical fluid. These methods therefore must be implemented before (before filling the bag) or after the bag is used (after prior draining of the biopharmaceutical fluid).
When these methods are performed before the bag is used but after its sterilization, the introduction of gas or fluid into the bag during the integrity verification poses a risk to the bag sterility. In particular, the risk of contaminating the bag due to the integrity verification itself is often judged to be greater than the risk of the presence of a hole in the wall of the bag. Because of this risk, these methods are often avoided. When they are implemented, these methods require the use of a sterile port to connect the bag to the pressurization system, which not only poses the risk of loss of sterility, but also is often long and complex to implement.
Moreover, when these methods are implemented after the bag is used, the biopharmaceutical fluid remaining in the bag, for example remaining drops, could clog the holes in the wall of the bag, particularly if these are small in size, and therefore skew the results of the integrity verification. In addition, such physical methods are ineffective for detecting microleaks in the bag, for example holes smaller than two microns. Moreover, it is detrimental to detect possible contamination of the biopharmaceutical fluid of the bag after this fluid is used. In such cases the use of the fluid may have been improper, which is useful to know but can be a problem.
Also known is another type of method for verifying the integrity of a bag suitable for containing biopharmaceutical fluid, before or after its use. This type of method consists of a bacteriological test called a “Bacterial Challenge Test” (BCT) in which the bag is first filled with a culture medium. The bag is closed and then immersed in a bath comprising a bacteriological medium. After removal from the bath, the culture medium of the bag is cultured to detect whether bacteria are present, which implies a leak in the bag wall and the passage of bacteria to inside the bag.
However, the disadvantage of this other type of method is that it takes a long time to implement. In addition, in actual practice, this method is only implemented after use of the bag. Such a method cannot be implemented when the bag is filled with biopharmaceutical fluid, for example during use of the bag, and the risk of impacting the sterility of the bag is too high to implement it before the bag is used. In addition, the conditions for implementing this method are not constant or controlled with certainty. The method is therefore often imprecise and difficult to repeat under identical conditions.
There are also known devices for verifying the integrity of a bag that do not require performing an integrity verification. For example, patent EP 2,662,307 describes a device comprising a first inner envelope defining a first space and forming a bag stricto sensu intended for receiving a biopharmaceutical fluid. A second outer envelope defines a second space in which the first envelope is located. A tracer gas is located either in the first space or the second space, at a pressure different from that of the second space or first space respectively. A colorimetric detection layer is located in the space that is not that of the tracer gas and is responsive to the concentration of tracer gas that reaches it by changing from a first color to a second color. Thus if there is leakage from the first envelope, the colorimetric layer changes color which enables detecting a loss of seal of the bag at any desired moment after manufacture and in any event immediately before use.
However, such a bag does not allow verifying the integrity of the second envelope of the bag, which only serves to contain the tracer gas and not to protect the biopharmaceutical fluid. Also, the presence of the tracer gas and colorimetric detector is ineffective for determining whether the second envelope has remained fluidtight. In addition, prior to its use, the first envelope constituting the bag stricto sensu must be extracted from the second envelope. This device therefore only allows verifying the integrity of the first envelope prior to use of the biopharmaceutical fluid, and not during or after its use.
There is therefore a need, in the specific field of the invention, for effectively protecting a biopharmaceutical fluid in a bag. There is also a need to be able to test the integrity of such bag before, during, or after its use, simply and with the same level of reliability, or even with a higher level of reliability, than the methods currently known or used.